Please help, I can't delete this gmail account and it's driving me crazy.

Hi,

I have an old gmail account from a decade ago which has reached its data limit. In the past few weeks, I've been getting more and more error notifications that the emails sent to this address are "not being processed" correctly. I don't need any of the data associated with the account and I don't use it anymore, I just want to permanently delete it.

I followed the steps to delete just this single email account (one of several gmail accounts that I have). However, when I get to the final step, it won't delete it unless I enter an alternative email address. It will not accept my school email address, bc that is associated with Google. It won't let me use my other gmail addresses. I don't have any other email addresses. I even made a new gmail address to try to use and it wont accept that. How the hell do I delete this damn account?